The use of lasers for processing light includes conversion of light from one part of the electromagnetic spectrum to another part of the spectrum. Typically, such processing involves the use of a nonlinear crystal in which an intensive laser beam interacts with an input laser beam, resulting in an output laser beam having a wavelength that is different from the intensive laser beam and the input beam. An example of a system in which such processing is performed is described in European patent published as EP0301803.
A drawback with such a prior art system is that it is incapable of processing of input light that is incoherent. For example, imaging of spatially extended sources that emit or reflect incoherent light is impossible in such a prior art system.
Such a prior art system is also not advantageous when a high quality laser beam is desired. In order to produce a high quality beam, the beam can e.g. be spatially filtered through a pinhole or it can be coupled to a single-mode optical fiber. However, both of these schemes lead to a significant loss in power, i.e. they are not energy efficient.